The use of fiber reinforced/resin matrix composite materials in the manufacture of articles and components in becoming increasingly widespread in a number of industries, including the aircraft industry. Such composite materials include, for example, graphite fiber reinforced/epoxy resin matrix materials and glass fiber reinforced/polyimide resin matrix materials. In a common manufacturing procedure for producing articles and components from composite materials, a plurality of layers of the material are held onto a mold, and the mold with the lay-up thereon is placed in an autoclave to cure the resin matrix. During the curing process, the lay-up is covered by a vacuum pressure bag which transmits the autoclave pressure uniformly over the surface of the lay-up. The uniform pressure produces a high quality finished article or component and is particularly important in the manufacture of aircraft parts which must meet stringent tolerance limitations and/or structural strength requirements. In preparation for the curing procedure, a vacuum probe is positioned under the bag and is connected to a vacuum line. A vacuum is applied through the line and the probe is evacuate air between the bag and the lay-up. This urges the bag against the lay-up so that the desired uniform pressure will be achieved.
A number of problems have arisen in connection with the use of conventional vacuum probes. A major problem is that conventional vacuum probe structures do not provide a sufficiently reliable seal between the bag and the probe around the opening in the bag through which the probe extends. In a commonly used type of vacuum probe, the bag and an annular sealing gasket are clamped between two probe body parts. During the clamping procedure, the body parts are twisted relative to each other. This relative twisting tends to cause the bag to wrinkle or bunch and thereby prevent a reliable seal between the bag and the probe. Since the sealing surfaces are not visible, the presence of wrinkling or bunching cannot be detected and the quality of the seal cannot be inspected visually. If the seal is lost during the curing process, the entire lay-up must be discarded. The discarding of lay-ups adds significantly to the overall cost of producing the parts.
Conventional probes are relatively difficult and time consuming to use. They include a plurality of parts which must be assembled each time the probe is used. The parts can become separated from each other between uses. Therefore, even more time may be required to locate the parts before the probe can be assembled for use. Conventional probes are also relatively expensive to manufacture because of the plurality of parts, the relatively complex structure, and the need to machine the sealing surfaces. In addition, although excess resin from the lay-up is usually absorbed by a breather layer positioned between the bag and the lay-up and an extra pad of breather material is conventionally positioned under the probe, resin from the lay-up can get into the probe. The resin can foul the screw connections of the probe and thereby necessitate either an expensive cleaning procedure or the discarding of the entire probe. All of these factors add to the overall cost of manufacturing the parts.
Still another problem associated with the conventional vacuum probe design is that the entire vacuum line quick connect/disconnect fitting is positioned above the sealing surfaces, and therefore, the probe has a high profile. Vacuum hoses are heavy and must stretch over a long distance during the curing procedure. The relatively high probe profile creates relatively high leverage tending to tip the probe over during the curing process. A tipped probe can mar the surface of the lay-up and create pressure voids. This ruins the lay-up so that it must be discarded.
One approach to solving the problem of unreliable seals is to modify the basic two-part body and gasket probe structure described above. Examples of modifications that improve seal reliability are providing a pressure plate and lock ring to seal against the gasket, and providing concentric seal ridges on the probe top. In the latter example, the ridges are machined into the probe top and seal into the gasket to allow it to slide over the bag. Another type of two-part probe body developed by the assignee of the applicant is the subject matter of a copending U.S. patent application Ser. No. 06/901,855, filed Aug. 29, 1986, in the name of Matin et al. and entitled "Non-Metallic Vacuum Probe". In the probe disclosed in that application, a bearing washing is positioned adjacent to the gasket to avoid twisting of the bag upon assembly of the probe. The two parts of the probe body are tightened together by twisting the upper body part. The body parts engage each other by a ramp and lug arrangement. The upper body part extends down through a central opening in the lower body part and has a center passageway that borders on and communicates with an indentation on the bottom surface of the lower body part.
Vacuum probe arrangements used in the manufacture or repair of composite material parts are disclosed in U.S. Pat. No. 3,666,600, granted May 30, 1972, to S. Y. Yoshino; and U.S. Pat. No. 4,554,036, granted Nov. 19, 1985, to C. M. Newton, U.S. Pat. No. 2,411,743, granted Nov. 26, 1946, to H. G. Morner discloses a vacuum connection on a bag used in molding plastic-bonded sheet material, such as plywood. Apparatus for evacuating bags of food for home freezing is disclosed in U.S. Pat. No. 4,018,253, granted Apr. 19, 1977, to S. I. Kaufman. The open end of the bag is pulled through a hollow retainer and is sealed between the retainer and a cap to which an evacuation tube is connected. U.S. Pat. No. 4,417,638, granted Nov. 29, 1983, to B. F. Harvey, discloses a self-sealing elastomeric grommet for the rigid portion of an air pallet which has a bayonet connection to an air supply nozzle.
Molding apparatus in which the edge of an internal pressure bag around the opening in the bag is positioned in a groove or clamped is disclosed in U.S. Pat. No. 54,204, granted Apr. 24, 1866, to J. L. Presbrey; U.S. Pat. No. 3,137,898, granted June 23, 1964, to E. E. Geringer; U.S. Pat. No. 3,610,563, granted Oct. 5, 1971, to P. E. Allen; and U.S. Pat. No. 3,674,394, granted July 4, 1972, to A. J. Wiltshire. In the Geringer and Allen apparatus, fibrous material is positioned between the bag and the mold, and air is driven out of the material through a vent by the introduction of resin. In the Wiltshire apparatus, a sealing ring is positioned around the circumference of a sliding core of the air supply fitting between the material being molded and the mold. The core is driven outwardly to a final molding position by pressure supplied to the bag. In this position, the sealing ring is received in a sealing ring seat provided between the counterbore in which the fitting slides and the inner mold surface. The sealing ring prevents resin from entering the counterbore and fouling the sliding surface of the core.
Other types of connections between a pressure bag and an air supply fitting are shown in U.S. Pat. No. 1,784,817, granted Dec. 16, 1930, to A. E. Bronson; and U.S. Pat. No. 2,999,272, granted Sept. 12, 1961, to E. P. Warnken. Molding apparatus in which the outer and/or inner periphery of a pressure diaphragm is clamped is disclosed in U.S. Pat. No. 286,693, granted Oct. 16, 1883, to J. Fried; and U.S. Pat. No. 2,962,757, granted Dec. 6, 1960, to C. O. Slemmons et al. Fried also discloses an air supply hose coupling to a chamber above the diaphragm. In the Slemmons et al. apparatus, air is exhausted from the space between the upper mold portion and the workpiece and from the space between the workpiece and the diaphragm. A diaphragm or gasket-like member with peripheral edge portions that are received in a groove or are clamped are disclosed in U.S. Pat. No. 2,322,043, granted June 15, 1943, to J. C. McCune; U.S. Pat. No. 2,944,523, granted July 12, 1960, to F. A. Werstein; U.S. Pat. No. 3,187,590, granted June 8, 1965, to J. E. Duggan; and U.S. Pat. No. 3,410,144, granted Nov. 12, 1968, to J. L. Noz et al. Grommet-like annular fittings clamped to sheet material are disclosed in U.S. Pat. No. 4,626,122, granted Dec. 2, 1986, to B. Harrison et al.; and French Pat. No. 1,194,397, published Nov. 9, 1959, in the name of R. Discry.
The above-cited patents and the prior art that is disclosed and/or cited therein should be studied for the purpose of putting the present invention into proper perspective relative to the prior art.